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copied!<pre><code>**Are there any cases where we do down casting of objects** </code></pre> <p>The purpose of dynamic_cast is to perform casts on polymorphic types. For example, given two polymorphic classes Band D, with D derived from B, a dynamic_cast can always cast a D* pointer into a B* pointer. This is because a base pointer can always point to a derived object. But a dynamic_cast can cast a B* pointer into a D* pointer only if the object being pointed to actually is a D object.</p> <pre><code>**`Is there any better way to achieve the same`** </code></pre> <p>Perhaps the most important of the new casting operators is dynamic_cast. The dynamic_cast performs a run-time cast that verifies the validity of a cast.</p> <p>1) Your class is not polymorphic.A class that declares or inherits a virtual function is called a polymorphic class</p> <p>2) Syntax of dynamic_cast is <strong>dynamic__cast (expr)</strong></p> <p><strong>1st Edit :</strong></p> <p>Try like this , it will work</p> <pre><code>class A { public: A(); virtual ~A();// Notice here i have put virtual }; class AImpl : public A { public: AImpl(A *obj); ~AImpl(); }; class Helper { public: Helper(){} static bool doWork(A *obj) { AImpl *objImpl = dynamic_cast<AImpl*> (obj); return true; } }; </code></pre> <p>Study this example : </p> <pre><code>class Base { public: virtual void f() { cout << "Inside Base\n"; } // ... }; class Derived: public Base { public: void f() { cout << "Inside Derived\n"; } }; int main() { Base *bp, b_ob; Derived *dp, d_ob; dp = dynamic_cast<Derived *> (&d_ob); if(dp) { cout << "Cast from Derived * to Derived * OK.\n"; dp->f(); } else cout << "Error\n"; cout << endl; bp = dynamic_cast<Base *> (&d_ob); if(bp) { cout << "Cast from Derived * to Base * OK.\n"; bp->f(); } else cout << "Error\n"; cout << endl; bp = dynamic_cast<Base *> (&b_ob); if(bp) { cout << "Cast from Base * to Base * OK.\n"; bp->f(); } else cout << "Error\n"; cout << endl; dp = dynamic_cast<Derived *> (&b_ob); if(dp) cout << "Error\n"; else cout << "Cast from Base * to Derived * not OK.\n"; cout << endl; bp = &d_ob; // bp points to Derived object dp = dynamic_cast<Derived *> (bp); if(dp) { cout << "Casting bp to a Derived * OK\n" << "because bp is really pointing\n" << "to a Derived object.\n"; dp->f(); } else cout << "Error\n"; cout << endl; bp = &b_ob; // bp points to Base object dp = dynamic_cast<Derived *> (bp); if(dp) cout << "Error"; else { cout << "Now casting bp to a Derived *\n" << "is not OK because bp is really \n" << "pointing to a Base object.\n"; } cout << endl; dp = &d_ob; // dp points to Derived object bp = dynamic_cast<Base *> (dp); if(bp) { cout << "Casting dp to a Base * is OK.\n"; bp->f(); } else cout << "Error\n"; return 0; } </code></pre>

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